Update implementation of atomics with latest Chromium version but use compiler builtin atomics

src/base/atomicops.h

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // The routines exported by this module are subtle.  If you use them, even if
 // you get the code right, it will depend on careful reasoning about atomicity
 // and memory ordering; it will be less readable, and harder to maintain.  If
 // you plan to use these routines, you should have a good reason, such as solid
 // evidence that performance would otherwise suffer, or there being no
 // alternative.  You should assume only properties explicitly guaranteed by the
 // specifications in this file.  You are almost certainly _not_ writing code
 // just for the x86; if you assume x86 semantics, x86 hardware bugs and
 // implementations on other archtectures will cause your code to break.  If you
 // do not know what you are doing, avoid these routines, and use a Mutex.
 //
 // It is incorrect to make direct assignments to/from an atomic variable.
 // You should use one of the Load or Store routines.  The NoBarrier
 // versions are provided when no barriers are needed:
 //   NoBarrier_Store()
 //   NoBarrier_Load()
 // Although there are currently no compiler enforcement, you are encouraged
 // to use these.
 //
 
 #ifndef V8_BASE_ATOMICOPS_H_
 #define V8_BASE_ATOMICOPS_H_
 
 #include <stdint.h>
+
+// Small C++ header which defines implementation specific macros used to
+// identify the STL implementation.
+// - libc++: captures __config for _LIBCPP_VERSION
+// - libstdc++: captures bits/c++config.h for __GLIBCXX__
+#include <cstddef>
+
+#include "src/base/base-export.h"
 #include "src/base/build_config.h"
 
-#if defined(_WIN32) && defined(V8_HOST_ARCH_64_BIT)
+#if defined(V8_OS_WIN) && defined(V8_HOST_ARCH_64_BIT)
 // windows.h #defines this (only on x64). This causes problems because the
 // public API also uses MemoryBarrier at the public name for this fence. So, on
 // X64, undef it, and call its documented
 // (http://msdn.microsoft.com/en-us/library/windows/desktop/ms684208.aspx)
 // implementation directly.
 #undef MemoryBarrier
 #endif
 
 namespace v8 {
 namespace base {
@@ skipping 85 matching lines @@
 void Acquire_Store(volatile Atomic64* ptr, Atomic64 value);
 void Release_Store(volatile Atomic64* ptr, Atomic64 value);
 Atomic64 NoBarrier_Load(volatile const Atomic64* ptr);
 Atomic64 Acquire_Load(volatile const Atomic64* ptr);
 Atomic64 Release_Load(volatile const Atomic64* ptr);
 #endif  // V8_HOST_ARCH_64_BIT
 
 }  // namespace base
 }  // namespace v8
 
-// Include our platform specific implementation.
-#if defined(THREAD_SANITIZER)
-#include "src/base/atomicops_internals_tsan.h"
-#elif defined(_MSC_VER) && (V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64)
+#if defined(V8_OS_WIN)
+// TODO(jfb): The MSVC header includes windows.h, which other files end up
+//            relying on. Fix this as part of crbug.com/559247.
 #include "src/base/atomicops_internals_x86_msvc.h"
-#elif defined(__APPLE__)
-#include "src/base/atomicops_internals_mac.h"
-#elif defined(__GNUC__) && V8_HOST_ARCH_ARM64
-#include "src/base/atomicops_internals_arm64_gcc.h"
-#elif defined(__GNUC__) && V8_HOST_ARCH_ARM
-#include "src/base/atomicops_internals_arm_gcc.h"
-#elif defined(__GNUC__) && V8_HOST_ARCH_PPC
-#include "src/base/atomicops_internals_ppc_gcc.h"
-#elif defined(__GNUC__) && (V8_HOST_ARCH_IA32 || V8_HOST_ARCH_X64)
-#include "src/base/atomicops_internals_x86_gcc.h"
-#elif defined(__GNUC__) && V8_HOST_ARCH_MIPS
-#include "src/base/atomicops_internals_mips_gcc.h"
-#elif defined(__GNUC__) && V8_HOST_ARCH_MIPS64
-#include "src/base/atomicops_internals_mips64_gcc.h"
-#elif defined(__GNUC__) && V8_HOST_ARCH_S390
-#include "src/base/atomicops_internals_s390_gcc.h"
 #else
-#error "Atomic operations are not supported on your platform"
+#include "src/base/atomicops_internals_portable.h"
 #endif
 
 // On some platforms we need additional declarations to make
 // AtomicWord compatible with our other Atomic* types.
-#if defined(__APPLE__) || defined(__OpenBSD__) || defined(V8_OS_AIX)
+#if defined(V8_OS_MACOSX) || defined(V8_OS_OPENBSD) || defined(V8_OS_AIX)
 #include "src/base/atomicops_internals_atomicword_compat.h"
 #endif
 
 #endif  // V8_BASE_ATOMICOPS_H_